Non-metal oxides are acidic in nature. When a base reacts with non-metal oxide, both neutralize and produce corresponding salt and water .
Base + Non metal oxide ⟶ Salt + Water
2 Ca(OH)2 + CO2 ⟶ CaCO3 + H2O
The reaction between carbon dioxide and calcium hydroxide (lime water) . Calcium hydroxide, which is a base, reacts with carbon dioxide to produce a salt and water. Since this is similar to the reaction between a base and an acid, we can conclude that non metallic oxides are acidic in nature.